Tracheal intubation with an oral airway (oral tracheal airway) for ventilation of a patient's lungs is an operation of critical importance. An incorrect intubation, in which the airway is inserted into the oesophagus instead of the trachea, will result in anoxia, brain damage, and death as air fails to reach the lungs. The patient s lungs are completely cut off from oxygen if the airway is wrongly inserted.
Correct intubation is so important that only an anesthesiologist or pulmonologist is allowed to perform it, even though the operation is actually a very simple one. As a result, patients who needed an immediate tracheal intubation have died while waiting for a specialist physician to arrive. Even though tests are available to indicate incorrect intubation (for example, testing for exhaled carbon dioxide, or measuring blood oxygenation) there is still grave danger.
One conventional intubation techniques uses a fiber-optic bronchoscope. Conventional intubation with a fiber-optic bronchoscope is pictured in the videotape "The Difficult Airway, Part III--Fiberoptic Intubation" from the American Society of Anesthesiologists, which is incorporated herein by reference as non-essential material.
First, an airway intubator is inserted through the mouth; it reaches to the back of the mouth area near the soft palate. The airway intubator is basically a relatively rigid, curved plastic tube. Its inner diameter is large enough to accept both an endotracheal tube and, within that, the fiber-optic bronchoscope. The endo-tracheal tube is a more flexible plastic tube through which the lungs will eventually be ventilated. The fiber-optic bronchoscope is smaller across than the inside diameter of the endo-tracheal tube.
The fiber-optic bronchoscope is inserted into the endo-tracheal tube outside of the patient, and then the physician guides the fiber-optic bronchoscope through the airway intubator and thence through the vocal cords. The fiber-optic bronchoscope is inflexible enough that its tip can be manipulated inside the patient by the physician's twisting and bending the protruding proximal portion. The fiber-optic bronchoscope may include an eyepiece for viewing, or may be connected to a TV monitor.
Fiber-optic technology is disclosed by Pirak et al, U.S. Pat. No. 5,400,771, and by Feldstein et al, U.S. Pat. No. 5,347,987, both of which are incorporated herein by reference in their entireties. The fiber optic bundle, including fibers for both image transmission to the TV camera and light transmission into the oral opening, are attached to the airway.
Pirak et al at column 4, lines 63-68, discloses that the physician can manipulate a fiber-optic member 12 while watching the image on a TV monitor.
Some endoscopes of the type incorporating fiber optics also include guide or control wires that allow the curvature of the endoscope to be varied. The controls can be activated either by hand turning of knobs or by automatic adjustment with solenoids, stepper motors, and so on, of the same type of controls. Conventional endoscope controls may also include automatic feed mechanisms that advance or retract the tip of the endoscope.
The incorporated Feldstein et al patent shows automatic control of a fiber-optic device by controls labeled 18 and 20. Television cameras have been connected to computers. The Feldstein patent discloses a computer digitizing the TV image from an endoscope fiber bundle and using the digitized image to detect motion of the endoscope away from a fixed position. Wire-controlled endoscopes are commonly used in industrial applications.
This technology is also disclosed in the following U.S. patents dealing with medical applications, all of which are entirely incorporated herein by reference: U.S. Pat. Nos. 5,506,912 to Nagasaki et al; 5,492,131 to Galel; 5,417,210 to Funda et al; and 5,018,509 to Suzuki et al.
Prior workers have used a computer to analyze the image from an endoscope and to control the position of the endoscope according to the computer's analysis of the image; but the programs they have developed are not at all suited to the task of tracheal intubation, and no automatic endotracheal intubation apparatus or method is now known.
As shown in the incorporated videotape, the tracheal opening, the larynx, presents a distinctive appearance: a strongly defined V-shape formed by the left and right vocal cords. No previous workers have used this distinctive shape, or any similar shape, for guiding an endoscope. Thus, the most distinctive aspect of the tracheal opening has been neglected by previous workers in the field.
For example, U.S. Pat. No. 4,910,590 to Gillies et al discloses automatic guidance of an endoscope according to illumination, distinguishing the center of a body tube (intestine) according dark and light ring-shaped areas in the image. Such image analysis would be useless in tracheal intubation.
The conventional techniques and apparatus have not overcome the problems of occasional incorrect intubation due to human error by physicians, or of intubations not being performed at all due to the absence of a qualified physician when needed. Even though the intubation is performed by a highly trained and experienced physician with the aid of a television and precise manual controls, incorrect intubations will always occur until automatic intubation guidance is provided to supplement or supplant human guidance.